1. Field of Invention
The present invention relates to devices and methods for carbonating beverages, more particularly to a portable home carbonator and a method of carbonating a predetermined quantity of premixed beverage.
2. Description of the Prior Art
The volume of carbon dioxide in a finished beverage is an important factor in its acceptability by the consumer, because the quantity of carbon dioxide dissolved in the beverage is what gives the beverage its sparkle, and governs the length of time, along with such other factors as temperature, that the beverage will continue to effervesce. Some beverages taste better with high carbonation, for example, ginger ales. Others taste better with low carbonation, for instance orange flavors. Most drinks, however, will have carbonation of between 3 1/2 to 4.0 volumes of carbon dioxide, particularly cola drinks.
Henry's law states that the amount of the gas dissolved in a given volume of a solvent at constant temperature is directly proportional to the pressure of the gas with which it is in equilibrium. According to this law, the amount of carbon dioxide dissolved by water at a given temperature is proportional to the pressure of the carbon dioxide on the water. This law is, however, conditioned by the nature of the molecule as it exists in the gaseous state and as it exists in solution. In the instance of carbon dioxide, as far as carbonated drinks are concerned, variations from Henry's law are not large.
At atmospheric pressure, the amount of carbon dioxide dissolved by water will depend solely on the temperature. This solubility is greater at lower temperatures than at higher temperatures. The unit of measurement that has been adopted by the beverage and bottling industry as standard is the volume. The volume is defined as the amount of gas in milliliters that a given volume of water will absorb at atmospheric pressure, (760 mm. of mercury) and 60.degree. F. (15.5.degree. C.). These are arbitrary points set by convention. This condition registers as zero on the scale of gauges commonly used to measure the volumes of carbon dioxide absorbed in carbonated beverages. Thus at 60.degree. F. and 1 atmosphere beverage water will absorb 1 volume of carbon dioxide, represented as zero on carbon dioxide gauges. When the pressure is increased to approximately 15 p.s.i. (one additional atmosphere) the water will absorb two volumes of the gas and for each additional 15 p.s.i. or atmospheres of pressure, an additional volume of carbon dioxide will be absorbed. Reduction of the temperature will, as mentioned, permit the water to dissolve greater amounts of carbon dioxide. When the temperature is reduced to 32.degree. F. (0.degree. C.), 1.7 volumes of carbon dioxide will be absorbed and for each additional increase of 15 psi of pressure, there will be an additional absorption of 1.7 volumes.
Carbonators used in the carbonated beverage industry are devices by means of which a large surface of water can be exposed to carbon dioxide gas under pressure. The combination of large surface and pressure enables water to absorb the gas quickly. Commercial carbonators vary in capacity from 250 to 3,600 gallons per hour.
One of the types of carbonators used in the industry is known as the "CEN Saturator." In this device, carbon dioxide gas enters through a gas connection and permeates the tank at operating pressure. Cold water from a water refrigerator is pumped into the tank through a water inlet, forced up a hollow center pipe column, and is then ejected through a specially designed nozzle as a smooth flowing sheet of water. The water is spread outward from the nozzle so that it flows over the underside of an inverted film plate. The water flows smoothly downward towards the center column over the film plate immediately below. This action is repeated continuously, the water at all times flowing as a thin film from plate section to plate section until it runs off the skirt of the lowest film plate into the carbonated water storage area at the bottom of the carbonator tank.
Another type of carbonator cools and carbonates at the same time. In this type of equipment, warm, uncarbonated water enters at the top going into a distribution pan from which it flows downward over stainless-steel cooling plates becoming carbonated with a carbon dioxide being admitted from the side. The cooled, carbonated water flows to a reservoir from which it can be conducted to the filler, at about 34.degree. F.
In more recent years, there has been an expansion of carbonated beverage dispensing from fountain dispensers. In an open-cup dispense, the final drink is made by the dispenser itself. A machine is actuated which consecutively drops a cup or container into position below an outlet port, pumps prepared syrup and carbonated water to a mixing chamber where the drink is mixed, and then releases the mixed drink to the container. In such dispensing equipment, water is carbonated as needed.
Numerous devices have been described for the carbonation of water in non-portable arrangements. For example, U.S. Pat. No. 2,339,640 (Holinger); U.S. Pat. No. 2,314,984 (Hudson); U.S. Pat. No. 3,240,395 (Carver); U.S. Pat. No. 3,752,452 (Iannelli); U.S. Pat. No. 3,960,164 (Kelley); U.S. Pat. No. 4,028,441 (Richards); U.S. Pat. No. 4,148,334 (Richards); and U.S. Pat. No. 4,304,736 (McMillin). The McMillin reference is directed to a method and apparatus for making and dispensing carbonated beverage utilizing propellant carbon dioxide gas for carbonating. The patent discloses a carbonator comprising a pressure vessel having a reservoir for carbonated water, and a gas base above the reservoir. Carbon dioxide gas and water are sprayed ino the head space through a nozzle. The high pressure source of carbon dioxide is connected through a conduit to a gas outlet fluidly connected into the carbonator gas base, and is provided with a storage pressure regulator for regulating a predetermined pneumatic storage pressure within the carbonator. An automatic venting valve is placed in fluid communication with the carbonator gas base, and vents gas from the headspace when the pressure in the carbonator exceeds the preset pressure of the storage pressure regulator. The storage regulator is set at a predetermined storage pressure of 25 psig which is less than the propellant pressure, and which gives an equilibrium saturation in the carbonator of about 41/2 volumes of carbonation at 0.degree. C. One of the disadvantanges of the McMillin device is that it is not portable, and does not provide the necessary carbonation in a short time, which is desired in a home carbonating unit. For that reason, the McMillin device requires a reservoir which is continuously filled, and depends upon carbonation taking place a nozzle which injects carbon dioxide gas and water.
Portable carbonation devices, in general, are quite old in the art. U.S. Pat. No. 565,922 (Prax) discloses a syphon bottle for carbonation having a removable lower part adapted to contain powders which when moistened, evolve the carbonating gas. Norwegian patent 52210 (Bryn), illustrates a device used for the carbonation of beverage in a bottle. In that device a cylinder containing CO.sub.2 gas is placed in a housing and disposed in communication with a tube, contained inside a bottle. Gas from the CO.sub.2 cannister enters the tube, and is then bubbled through the bottom of the bottle. One of the disadvantages of this device is that only a limited amount of carbonation can be achieved by this process in a reasonable time, because as the pressure in the headspace of the bottle increases, the volumetric rate of CO.sub.2 through the liquid decreases.
Other references disclose how to achieve carbonation from by-products of a chemical reaction between citric acid and calcium carbonate. These include U.S. Pat. No. 3,480,403 (Hovey); U.S. Pat. No. 3,476,520 (Hovey); U.S. Pat. No. 2,600,901 (Meldau); U.S. Pat. No. 2,591,990 (Westum); U.S. Pat. No. 3,492,671 (Hovey).
U.S. Pat. No. 4,347,783 (Ogden) shows a beverage carbonator device comprising a pair of containers communicating through a spring biased valve, and having one of the containers in communication with a tube extending vertically and then horizontally in a container having liquid to be carbonated. The device illustrated is screwed on at the top of the container and provides a tight, leak proof seal with the container holding the liquid to be carbonated. Similarly, U.S. Pat. No. 4,040,342 (Austin), describes a carbonator including an absorber tank having a bottom, side walls, and a top joined together to form an airtight tank to hold a body of water. Carbon dioxide is injected into the water and the pressure of the gas above the water maintains the carbonation and provides for expulsion of the carbonated water.
Other arrangements for the carbonation of beverage include U.S. Pat. No. 4,186,215 (Buchel); U.S. Pat. No. 3,888,998 (Sampson, et al.); U.S. Pat. No. 4,025,655 (Whyte, et al.); and U.S. Pat. No. 4,110,255 (Liepa, et al.).
One of the disadvantages of the devices described in the references listed above is that they fail to provide the necessary carbonation in a reasonable time. Devices which are open to atmospheric pressure, such as the devices listed in the latter four references, fail to provide the degree of carbonation necessary for typical soft drinks, which as stated above, will vary from three to four volumes.
Other references which are pertinent to portable carbonators are U.S. Pat. No. 3,953,550 (Gilbey); and U.S. Pat. No. 4,251,473 (Gilbey).